No battery, no robot. It really is that simple.
The moment you cut the cable and run on battery power, your robot goes from a desk ornament to something that can actually explore the world — and choosing the right cell makes the difference between a robot that lasts all day and one that gives up after five minutes.
What is a Battery?
A battery is an electrochemical device that stores energy and releases it as electricity. For robot builders, the three types you’ll encounter most are:
- Alkaline AA/AAA — cheap and easy to buy, but voltage drops as they discharge, and they can’t deliver big current spikes without sagging. Fine for low-power prototypes.
- NiMH rechargeables — a better choice than alkalines for most beginner robots. Reusable, reasonably cheap, and they handle motor loads well.
- LiPo (Lithium Polymer) — the favourite for RC cars, drones, and performance robots. High energy density, flat discharge curve, and they can push serious current. Rated in milliamp-hours (mAh) and cell count (1S = 3.7 V, 2S = 7.4 V, etc.). Handle them carefully — they don’t like being over-discharged or punctured.
- 18650 Li-ion cells — the same chemistry as LiPo, but in a sturdy cylindrical can. Used in power banks and many off-the-shelf battery packs. Great for Raspberry Pi robots.
A useful rule of thumb: capacity (mAh) tells you how long; voltage tells your motors how fast.
Series and parallel
How you wire multiple cells decides what you get. Stack them in series and the voltages add (capacity stays the same). Wire them in parallel and the capacities add (voltage stays the same). The schematic symbol for a cell is a long line (+) and a short line (−):
SERIES — voltage adds PARALLEL — capacity adds
+─┤├──┤├──┤├─ − +─┬──┤├──┬─ −
3.7 3.7 3.7 │ │
├──┤├──┤
3 × 3.7 V = 11.1 V (3S) │ │
capacity unchanged └──┤├──┘
all 3.7 V, 3× the mAh
long line = + short line = −
A “3S” LiPo is three cells in series (11.1 V nominal); a “2P” pack is two cells in parallel for double the run-time. Many packs combine both — a “3S2P” gives you the higher voltage and the bigger capacity.
Why Robot Builders Care
Every component in your robot — microcontroller, motors, servos, sensors — draws current. Motors are the hungry ones. A stall current spike from a pair of DC motors can be five to ten times the running current, so a battery that looks adequate on paper can sag into a low-voltage reset at exactly the wrong moment.
You also need to match voltage to your system. A Raspberry Pi wants a stable 5 V; a motor driver might want 6–12 V. Often you’ll run two separate supplies, or use a buck converter to step voltage down from a single higher-voltage LiPo pack.
Wrong battery choice is behind a surprising number of “my robot acts weird” moments.
Get Started
The best starting point is to understand your options properly. Kevin’s deep-dive post Power up your robot projects walks through alkaline, NiMH, LiPo, solar, and even wireless charging.
Once you’re ready to put that knowledge into practice, the SMARS course shows you how a complete battery-powered wheeled robot fits together from scratch — including how the power wiring works.
For a broader picture of how batteries slot into the electronics of a full build, Robotics 101 covers the fundamentals that underpin every robot you’ll ever make.
A good first experiment: take any robot you’ve built, swap out plain alkalines for NiMH rechargeables, and notice how much more consistently the motors run. Then try a small LiPo pack (with the right protection circuit) and see what changes. Your robot will thank you.
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